WO2020087128A1 - Détection et diagnostic de défaillance de ferme solaire - Google Patents

Détection et diagnostic de défaillance de ferme solaire Download PDF

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Publication number
WO2020087128A1
WO2020087128A1 PCT/AU2019/051203 AU2019051203W WO2020087128A1 WO 2020087128 A1 WO2020087128 A1 WO 2020087128A1 AU 2019051203 W AU2019051203 W AU 2019051203W WO 2020087128 A1 WO2020087128 A1 WO 2020087128A1
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WIPO (PCT)
Prior art keywords
string
fault
strings
current
currents
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PCT/AU2019/051203
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English (en)
Inventor
Amit DHOKE
Rahul Sharma
Tapan Kumar Saha
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The University Of Queensland
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Publication date
Priority claimed from AU2018904145A external-priority patent/AU2018904145A0/en
Application filed by The University Of Queensland filed Critical The University Of Queensland
Priority to US17/290,134 priority Critical patent/US20230299715A1/en
Priority to EP19878817.6A priority patent/EP3874593A4/fr
Priority to AU2019370621A priority patent/AU2019370621A1/en
Publication of WO2020087128A1 publication Critical patent/WO2020087128A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H02S50/10—Testing of PV devices, e.g. of PV modules or single PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the present invention concerns a method and apparatus for detecting faults in large arrays of PV modules of PV power generation assemblies or as they are sometimes called“solar farms”.
  • FIG. 1 is a block diagram of a fault free, typical photovoltaic (PV) power generation assembly or“solar farm” 1 .
  • PV photovoltaic
  • the PV assembly 1 includes a PV array 3 that is comprised of n parallel strings 5- 1 ,...,5n, each comprised of m series connected PV modules 7-1 1 ,...,7-nm so that the array 3 includes a total of nm PV modules.
  • the PV modules 7 comprise solar panels which are each made up of a number of interconnected solar cells. Depending on the degree of solar radiation and the physical and electrical properties and interconnection of the solar cells of each panel, each PV module generates electricity, for example according to the specifications set out in Table 1 .
  • Module peak power (MPP) (P max) 240W Open circuit voltage(Voc) 37.2V Short Circuit current(lsc) 8.37A Voltage at MPP 30.4V Current at MPP 7.89A
  • Each string 5-1 ,...,5-n has a positive end (at the top of the string as depicted in Figure 1 ) and a negative end (at the bottom of the string as depicted in Figure 1 ) and includes a return or negative” line cable 9 from the negative end that runs along the PV modules to the positive end.
  • the strings 5-1 , ... ,5-n are connected in parallel to an Inverter 13 via over-current protection devices 8-1 ,..., 8-n, connection box 1 1 and ground fault protection device 12, all of which are well known in the prior art.
  • Inverter 13 converts the DC power from the strings 5-1 ,...,5-n into AC power which is suitable for feeding into a grid utility 15.
  • the voltage generated between the ends of each string 5 is mxV where V is the voltage across each individual module 7.
  • the total current flowing out of the array is nxl where I is the current through each string. Due to the structure of array 3, the same current is produced by each module in the string and each string in the array has the same voltage across it. For the given array 3, total output power ( P OM ) can be evaluated as (mxV) x (nxl).
  • Fault F1 comprises a short circuit (or low resistance path) between the interconnection of PV modules 7-22 and 7-23 and the return cable 9-2.
  • Fault F1 effectively causes PV modules 7-23,..., 7-2m of string 5-2 to be bypassed so that only PV modules 7-21 and 7- 22 contribute to current output for string 5-2. Consequently string 5-2 is“mismatched” relative to the other, normally functioning strings.
  • the accumulation of faults such as F1 causes a reduction in the output of the solar array 3 and thus of the overall assembly 1 .
  • PV power generation assembly 1 may have hundreds or even thousands of PV modules, faults such as F1 may go undetected until the operation of the PV assembly 1 has been substantially compromised.
  • a method for detecting a fault affecting one or more strings of a plurality of strings each comprised of a number of PV solar modules in series comprising: determining a representative string current for currents of the plurality of strings;
  • the method includes applying sensor assemblies to each of the strings for measuring respective currents therethrough.
  • the method includes receiving a measurement signal from each of the sensor assemblies across an electronic data network.
  • the method includes operating a computer to issue an alarm to a computational device of an operator upon deeming the one or more strings to be subject to a fault.
  • the representative string current comprises a mean 1 « of the currents of all of the strings and the plurality of strings comprise strings h,...,U and the string current through the i th string is h and the sum of string currents I a of the currents of the plurality of strings is: and the mean current for each string of the array is:
  • the representative string current may comprise a value other than the average string current, for example, it may comprise a mid-range value of string currents of the plurality of strings.
  • the deeming of the one or more strings having currents that are outliers to the representative string current by more than a threshold value to be subject to a fault includes determining, for each string current a residual n,...,r n where:
  • the method preferably includes deeming an intra-string fault to be present in the i th string according to:
  • the method includes deeming a cross string-fault to be present between i th and j th strings according to:
  • the threshold value is determined by measuring currents through each string in relation to a representative string current for currents of the plurality of strings when all of the strings are in a no-fault condition.
  • the supremum and Th is the greatest lower bound on the norm bounded values of string current residuals.
  • the method includes monitoring a current through each string to determine the representative string current.
  • the method preferably includes identifying a fault location in terms of a number of PV modules along a string that is deemed to be subject to a fault.
  • the method includes identifying the fault location as a function of current through the string that is subject to the fault and of solar irradiance upon the PV modules.
  • the fault is identified to be a cross-string fault and the method preferably involves initially identifying the fault location on a first one of the cross-string fault affected strings and then using that fault location to find a fault location on the second of the cross-string fault affected strings.
  • the method includes generating the function by modelling an array for a plurality of faults.
  • the function may be stored as a look up table.
  • a fault detection assembly for a PV solar generation assembly comprised of an array of PV modules including a plurality of series PV module strings connected in parallel, the fault detection assembly including:
  • a processing arrangement in communication with the current sensors for receiving values of the string currents therefrom;
  • a memory device accessible to the processing arrangement containing instructions for execution by the processing arrangement including instructions for:
  • the memory device further includes instructions for the processing arrangement to determine one or more fault locations for the one or more strings deemed to be subject to the fault.
  • the memory device further includes instructions for identifying the one or more fault locations as a function of current through one or more strings that are subject to the fault and of solar irradiance upon the PV modules.
  • a PV solar generation assembly including:
  • a processing arrangement in communication with the current sensors and arranged to detect intra-string faults and/or cross-string faults based upon one or two of the string currents exceeding a threshold value.
  • FIG. 1 is a block diagram of a photovoltaic (PV) electricity generation assembly connected to a grid utility.
  • PV photovoltaic
  • Figure 2 is a block diagram of the PV electricity generation assembly exhibiting a fault along one of the strings of its array of PV modules.
  • FIG. 3 is a block diagram of a fault detection assembly according to a preferred embodiment of the invention shown in use and connected to the PV electricity generation assembly of Figure 2.
  • Figure 3A is a block diagram of a server of the fault detection assembly of
  • Figure 4 is a flowchart of a method according to a preferred embodiment of the present invention.
  • Figure 5 is a graph of string current versus string number for a 4 x 4 PV module array showing the effect of a fault at each of four locations along a first string of the array.
  • Figure 6 is a diagram of a solar array corresponding to the graph of Figure
  • Figure 7 is a three dimensional graph of a function for determining fault location for each of a number of solar irradiation levels of a 15 x 4 array of solar PV modules.
  • Figure 8 is a block diagram of a solar array in which a cross-string fault is present.
  • Figure 9 is a chart illustrating the effect of a cross-string fault between two strings on string current for five different locations of the fault.
  • Figure 10 is a diagram showing the first fault for the chart of Figure 9.
  • Figure 1 1 is a diagram showing the second fault for the chart of Figure 9.
  • Figure 12 is a diagram showing the third fault for the chart of Figure 9.
  • Figure 13 is a diagram showing the fourth fault for the chart of Figure 9.
  • Figure 14 is a diagram showing the fifth fault for the chart of Figure 9.
  • Figure 15 is a graph relating change in fault location to change in current for cross string faults for each of a number of irradiance levels.
  • Figure 16A is a graph indicated fault current magnitudes in a 3 x 3 array at a
  • Figure 16B is a graph indicating fault current magnitudes in a 5 c 3 array at a
  • Figure 16C is a graph indicating fault current magnitudes in a 7 x 3 array at a
  • Figure 16D is a graph indicating fault current magnitudes in a 9 c 3 array at a
  • a fault detection assembly 4 according to a preferred embodiment of the present invention that comprises a plurality of sensor assemblies 19-1 ,...,19-n such as current meters that each generate a measurement signal that in the presently described embodiment of the invention is conveyed to data network 21 and thence to a server 23.
  • Server 23 is programmed by computer program 27 to log the measurement signals in database 25 and processes them according to instructions stored in a computer program 27 for detecting faults in a manner that will be described.
  • the method that is described herein may be implemented on a microcontroller, programmable logic controller or other suitable processing platform.
  • FIG. 3A comprises a block diagram of the server 23 which is specially programmed with fault detection software product 27 to enable the server to undertake its various tasks as described herein so that a unique hardware and software combination is provided.
  • the server 23 includes a memory device in the form of secondary storage 47, which is typically implemented by a magnetic or solid state data drive and which stores a server operating system, for example Microsoft Windows Server and Ubuntu Linux Server are two examples of such an operating system.
  • server operating system for example Microsoft Windows Server and Ubuntu Linux Server are two examples of such an operating system.
  • the server 23 includes a main board 34 which includes circuitry for powering and interfacing to at least one processing arrangement in the form of at least one onboard central processing unit or“processor” or“microprocessor” 35.
  • the at least one onboard processor 35 may comprise two or more discrete processors or processors with multiple processing cores.
  • the main board 34 acts as an interface between CPUs 35 and secondary memory 47.
  • the main board 34 also communicates with random access memory device (RAM) 41 and read only memory (ROM) 43.
  • RAM random access memory
  • ROM read only memory
  • the ROM 43 typically stores instructions for a Basic Input Output System (BIOS) which the CPUs 35 access upon start up and which prepares the CPUs 35 for loading of the operating system 39 from secondary memory 47.
  • BIOS Basic Input Output System
  • the main board 34 will typically include a communications adapter, for example a LAN adaptor 53 that places the server 23 in data communication with a computer network such as the Internet 21 via a router or other suitable network interface device.
  • a communications adapter for example a LAN adaptor 53 that places the server 23 in data communication with a computer network such as the Internet 21 via a router or other suitable network interface device.
  • the server 23 may include a human-to-machine interface (HMI) in the form of keyboard 49, mouse 21 and display 48 which enables administrator 6 to directly enter commands, read output, and generally interact with the server as the CPUs 35 execute various operating system and application software instructions.
  • HMI human-to-machine interface
  • the administrator logs into the server 23 remotely over the Internet 21 or another data network and performs administrative tasks remotely using a local terminal 12 as the HMI.
  • the secondary storage 47 also stores the database 25 that is implemented by the fault detection program 27.
  • the server processor assembly 35 loads the operating system 39 and then loads the fault detection program 27.
  • the exemplary computer server 23 that is illustrated in Figure 3A comprises a discrete hardware machine that is suitably programmed.
  • the server may be implemented by a virtual machine, e.g. a“cloud server” that uses shared hardware resources of a “server farm” as required.
  • String current measurement data from sensor assemblies 19-1 , ... ,19-n may be transferred through a fibre optic cable to a control centre which, using a dedicated communication port, then streams the string current data to a cloud server that implements computer server 23 with high power computing capability.
  • the fault detection assembly is able to detect intra-string faults and also cross-string faults and is also able to determine locations of the faults along the fault-affected strings.
  • the server 23 is able to transmit the identity of the affected string or strings and fault location information across the network 21 to alert administrator 6 by means of the administrator’s networked device 23.
  • the value of the string current measured by each of the meters 19 is denoted as h, i e [1, n], where subscript‘f refers to the z* string measurement.
  • the array current and voltage are written as I a and V a , respectively and indicated on Figure 3 for example.
  • FIG. 4 is a block diagram of a flowchart of a method according to a preferred embodiment of the present invention.
  • the computer program 27 comprises machine readable instructions, which may be stored as non-transitory tangible instructions 59 on a magnetic 47 or optical drive 57 for example for reading by disk drive 52, for the server 23 to perform the method.
  • the server 23 receives measurements from sensors 19-1 , ... ,19-n of each of the string currents /;,...., for each of the strings 5-1 ,...,5-n.
  • the server 23 calculates the array current which is the sum of the string currents: and then calculates a representative string current in the form of a mean current for each string of the array, which is:
  • the representative string current may comprise another quantity other than the mean value, such as a mid-range value of string currents of the plurality of strings for example.
  • the server 23 deems a string having a current that is an outlier to the representative string current by more than a threshold value to be subject to a fault.
  • the server performs that step at box 33 by calculating, for each string current a residual n,...,r n where:
  • the server 23 deems an intra-string fault to be present or absent in the z* string of strings 5-1 ,..., 5-n according to:
  • threshold value is the threshold value and where the value of i is unique so that there is only one string that has a single residual value that has a magnitude greater than the threshold value.
  • the method that has been described makes reference to a threshold value against which the residuals n are tested.
  • the threshold value is determined based on measuring currents through each string in relation to a representative string current for currents of the plurality of strings when all of the strings are confirmed to be in a no-fault condition.
  • Th signifies the calculation of the greatest lower bound on the norm bounded values of string current residuals.
  • FIG. 5 is a chart that represents the effect of intra-string faults on the current produced by string 5-1 for each of four fault locations along that string based on the location of the fault ⁇ La i e [1, 4]) in a 4 x 4 array of solar modules.
  • Figure 6 illustrates the 4 x 4 array which is comprised of four parallel strings 5-1 ,..., 5-4 each with four series PV modules 7-1 1 ,...,7-44 and shows the locations LI, . . . ,IA at which faults may occur between the series PV modules 7-1 1 ,...,7-14 of string 5-1 and its return line 9-1 .
  • the voltage across string 5-1 is held at the non-faulted voltage V a and thus the voltage across each of the non-bypassed modules will increase proportionally to maintain the same voltage across all the strings.
  • the current h through the fault-affected string 5-1 is reduced if the fault is at level L1 and becomes increasingly negative as the fault location passes to L2, to L3 and thence to L4 due to backfeed current that flows from the no-fault strings 5-2, ..,5-4 to faulty string 5-1 to maintain the string voltages equal.
  • a fault location procedure is implemented by the server 23 to ascertain the likely location of the occurrence of the intra-string fault along the string.
  • the location of the fault, along with irradiance, number of modules in the string, number of strings in the array and ambient temperature collectively governs the level of fault current (/, ⁇ ) through the faulty string. Consequently the estimated fault location within the i th string can be expressed in functional form as follows: where denotes the estimated fault location within the i th string.
  • the values of m and n are fixed.
  • the temperature (T a ) is assumed constant considering it has a weak effect on current, hence on the fault location. Therefore, for a given PV array the expression (2) can be reduced to the following functional form: - (G S) ( 3 )
  • the range of G is taken to be between 400 W/m 2 - 1000 W/m 2 .
  • the choice of this range is practically meaningful for the Inventors because in their working location of Queensland, Australia nearly 75% - 90% of the time on a clear sky day the irradiance levels are within 400 W/m 2 - 1000 W/m 2 .
  • a 3-dimensional data set between -G- was obtained through a series of simulations performed using a simulation model developed in Matlab Simulink. It will be realised that other approaches to produce the regression function may also be used.
  • Various array configurations were implemented in Simulink including 4 x 4, 6 x 3 and 15 x 4 module arrays.
  • Fig. 7 graphically represents the data set obtained for the 15 x 4 configuration. The data set was obtained by running simulation sweep for various fault locations (between 1 to 15) and Solar irradiance values (between 400 W/m 2 - 1000 W/m 2 in the steps of 100) combinations and the corresponding string (fault) current levels.
  • fault location can be calculated at a given irradiance.
  • the fault characteristics show that string currents during 600 W/m 2 - 1000 W/m 2 are nearly linear. Most of the time on a clear sunny day the level of irradiance is above 600 W/m 2 . That can make fault detection more effective and appropriate to avoid false alarms. Flowever, the method of the preferred embodiment can still detect and locate the fault below 600 W/m 2 , though with less accuracy.
  • a PV array was arranged with four strings with each string having four modules connected in series. Sensor assemblies in the form of current sensors were placed at each string end to analyse the impact of line-line faults on string current magnitudes.
  • random intra-string faults were created by making short circuits at locations LI,...,L4 in string 5-1 of Figure 6.
  • the corresponding string currents and irradiation were measured. The results obtained from these experiments are summarized in Table 2.
  • the threshold value was calculated using Eq.1 in a no fault condition at a given irradiance.
  • Table 2 Estimated and actual fault locations with different irradiance.
  • Table 2 confirm the ability of a method according to an embodiment of the invention to accurately detect and locate intra-string line-line faults.
  • the accuracy in estimating the fault location was 85% or better in all cases.
  • the preferred method according to the present invention is capable of estimating the location with high level of accuracy at different irradiance levels.
  • the performance of the proposed fault detection and diagnosis method was also analysed in respect of a 6 x 3 PV array.
  • intra string faults were introduced at various locations within the first string sequentially from location 1 to location 6.
  • the fault detection and location estimation results are set out in Table 3.
  • the threshold was calculated using Eq. 1 and was 0.45 and 0.5 at 750 W/m 2 and 800 W/m 2 during fault free conditions respectively.
  • the Inventors’ investigations have brought them to the belief that the proposed approach is very useful for detecting and locating faults in different array configurations.
  • the expected fault location can provide the exact fault location after rounding of the L, values. Also, it is noticeable from the Table 3 that efficiency of estimated fault location increases with an increase in experimental fault location.
  • the preferred embodiment assumes irradiation levels between 700W/m 2 - 1000W/m 2 .
  • embodiments can detect faults in low irradiation with lower accuracy. Very low irradiation causes the fault currents to be too small to be readily detectable.
  • F1 of Figure 2 Another type of fault that may occur in a solar farm is a cross-string fault.
  • Fault F2 which is illustrated in Figure 8, is an example of a cross-string fault.
  • Delta location is preferably used: that is, the difference between fault locations on the two fault affected strings is determined.
  • delta location i.e. the difference in fault locations
  • exact location on each string is determined by determining the fault location on one of the strings by following the same approach as the intra-string faults, and using delta location value to determine location on the second faulty string.
  • a cross-string fault such as F2 causes a current (indicated in Figure 8 as to flow through the fault from the higher potential point ⁇ L m.i on string S2) to the lower potential point ⁇ L m.i on string S3).
  • the preferred embodiment of the present invention encompasses a fault identification method and apparatus that is able to ascertain whether the fault is within a single string (i.e. an intra-string fault) or between two strings (i.e. a cross-string fault).
  • the proposed fault identification approach is based on the establishment of the number of string current outliers that are detected. A fault that is indicated by the presence of one outlier is deemed to be an intra-string fault (box 35 of Figure 4) and a fault that is indicated by the presence of two outliers (box 39 of Figure 4) is deemed to be a cross-string fault.
  • the residual n for a given string will depend on string currents affected by potential difference during different line-line faults with the threshold £n calculated based on the array size. Fault identification is established on the satisfaction of following two conditions: 1 ) If only one of the strings exhibits a residual that is greater than the threshold value then an intra-string fault is present. This condition is reflected in box 35 of Figure 4.
  • an intra-string fault is expected to result in one outlier, i.e. one string exhibiting n > £n while a cross string fault is likely to result in two outliers i.e. n > £n and h > £n for two different strings Si and S j .
  • intra-string faults only one string can be affected by lowering and/or reversing the direction of the string current while the currents of the remaining strings remain normal.
  • cross-string line-line faults the fault affected strings experience a current variation based on the number of PV modules that are effectively switched from one string to the other due to the cross-string fault. Based on the number of string outliers which is a function of the fault-affected currents, a fault can be identified as intra-string (a single outlier) or a cross-string (two outlier) fault.
  • FIG. 9 is a chart that shows the variation in string current h and h for two strings Si, S2 for each of five different cross-string faults, F21, F22, F23, F24 and F25 which are respectively illustrated in Figures 10 to 14.
  • fault F21 is between L2 on S1 and L1 on S2 as illustrated in Figure 10.
  • Fault F21 increases the current h out of string S2 and decreases the current h out of string Si. This change occurs due to the cross-string fault F21 electrically connecting panels 7-14 and 7-15 of Si to the negative side of PV module 7-24 of S2 so that current from PV modules 7-14 and 7-15 contributes to the current h that flows out of string S2. At the same time, the current contributed by PV modules 7-14 and 7-15 to the current h out of string Si « reduced.
  • the cross-string fault results in one of the affected strings effectively having a reduced number of modules and the other string having a greater number of modules.
  • the fault F21 in Figure 10 causes String 1 to gain a PV module 7-25 from string 2 and for string 2 to lose PV module 7-25.
  • a short circuit between two different locations of the string creates a potential difference between short circuited points. As a result, current flows from higher potential to lower potential.
  • the difference in current between the fault affected strings is a function of the voltages at the end points of the fault locations, when those voltages are measured prior to the fault occurring.
  • the string associated with one of the outliers will have a larger current than the string associated with the other of the outliers.
  • the string current (/;) changes with fault location (L;) at a given irradiation. From this observation, it is understood that the difference of the fault-affected string currents (Al) is proportional to the difference in fault locations (AL) given as per Eqs. (5) and (6).
  • the Inventors have conceived that this relationship can be used to formulate a fault location approach for a preferred embodiment of the present invention, which is implemented by server 23 under control of instructions comprising software product 27.
  • Fault locations at the i th and j th faulty strings are denoted as L, and L,.
  • the corresponding current measurements are h and Ij. Based on the measurements, the relationship established using relative location and current is given by
  • the fault location between the two strings vary the associated string current varies as well.
  • the fault location of one of the strings is estimated and the fault location in the second faulty string can be obtained using the equation (6).
  • DI and AL have a nearly linear relationship especially in the irradiance range between 700 W/m 2 to 1000 W/m 2 .
  • the linear relationship exists regardless of the fault locations. Consequently, if the string currents are known, the module mismatch percentage or number of bypassed modules ⁇ AL) can be estimated using the following expression,
  • Table 4 shows estimated values of slope (m) and intercept (b) for plotted lines in Fig. 15 at the respective irradiation.
  • Eq. (7) the expression is obtained for 4 x 4 array.
  • a similar expression can be obtained for any array size through DI and AL characteristics.
  • the expression for the likely location of the fault (Li) in the i th string can be obtained according to Eq. (6).
  • the Inventors created various cross-string fault combinations using MATLAB/Simulink and generated three dimensional data by following the same procedure that was previously discussed for intra string faults in relation to Figure 7. Similar to the procedure that was followed for intra-string fault analysis, a regression expression was derived for use in cross string fault location detection. By extracting the parameters of the regression function, likelihood location of the fault L t at given irradiance (G) was estimated using string current (/, ⁇ ). Once the location of the fault in the i th string was known, the location of the fault in the j th string could then be estimated using Eq. (7).
  • this section proposes approaches to re-model the expression to suit other PV array configurations with varying modules, strings and temperature.
  • Figures 16A -16D respectively represent current magnitudes with varying number of modules in a string (Fig. 16A) 3 x 3, (Fig. 16B) 5 x 3, (Fig. 16C) 7 x 3, (Fig. 16D) 9 x 3 and locations at 1000W/m 2 .
  • s 0 u denotes the slope of the line which characterises current versus location characteristics
  • s new represents the slope corresponding to the current versus location characteristics for the new array configuration for which the fault location expression is to be remodelled
  • m 0id and m mw represent number of modules in the existing string and new string, respectively.
  • n mtio denotes ratio of old and new strings numbers, old and new represents number of old and new strings respectively.
  • the estimated fault location expression for the new array size can be obtained by substituting Eq. (1 1 ) in Eq. (7).
  • the given approach was verified on 4 x 4 array and the results are shown in Table 8. The results confirm that the proposed approach is capable of generalising fault location estimation for n number of strings with good accuracy.
  • the string current may be affected only slightly with major change in T and is therefore usually ignored.
  • the proposed approach was verified by changing the Tas per Eq. (2) and keeping other parameters (G, m, n) constant. It was observed from the simulations that the temperature change has a negligible effect on the string currents which does not affect the fault detection and location.
  • methods according to embodiments of the present invention can be implemented by a suitably programmed server, for example server 23 as previously discussed or by a microcontroller or programmable logic controller (PLC), which monitors the string currents and diagnoses the fault.
  • server 23 for example server 23 as previously discussed or by a microcontroller or programmable logic controller (PLC), which monitors the string currents and diagnoses the fault.
  • PLC programmable logic controller
  • the server 23 continuously monitors the current values for each string that are transmitted to it by string current sensors 19-1 ,...,19-m across data network 21 .
  • the values are typically logged in database 25 along with the time and date that they are recorded.
  • the server 23 raises an alarm which is a term than encompasses simple notifications such as an electronic message that is transmitted across the data network 21 to a remote device 12 of an administrator 6.
  • administrator 6 Upon receiving the alarm message, which includes fault location information, administrator 6 is able to travel to the location of the fault in the solar array and take action to rectify the fault.
  • each of the strings consists of a number of series connected PV modules.
  • a PV module could comprises a single solar PV panel or a block of series and/or parallel connected solar PV cells, for example.

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  • Photovoltaic Devices (AREA)

Abstract

La présente invention concerne un ensemble de détection de défaillance pour un ensemble de génération d'énergie solaire photovoltaïque (PV) constitué d'un réseau de modules PV comprenant une pluralité de chaînes de modules PV en série connectées en parallèle, l'ensemble de détection de défaillance comprenant : une pluralité de capteurs de courant conçus pour surveiller des courants de chaîne respectifs desdites chaînes ; un agencement de traitement en communication avec les capteurs de courant pour recevoir des valeurs des courants de chaîne à partir de ceux-ci ; un dispositif de mémoire accessible à l'agencement de traitement contenant des instructions destinées à être exécutées par l'agencement de traitement, comprenant des instructions pour : déterminer un courant de chaîne représentatif pour des courants de la pluralité de chaînes ; considérer une ou plusieurs chaînes ayant des courants qui sont des valeurs aberrantes par rapport au courant de chaîne représentatif de plus d'une valeur de seuil comme étant soumises à une défaillance ; et émettre une alarme comprenant une identification de la ou des chaînes considérées comme étant soumises à la défaillance.
PCT/AU2019/051203 2018-10-31 2019-10-31 Détection et diagnostic de défaillance de ferme solaire WO2020087128A1 (fr)

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US17/290,134 US20230299715A1 (en) 2018-10-31 2019-10-31 Solar farm fault detection and diagnosis
EP19878817.6A EP3874593A4 (fr) 2018-10-31 2019-10-31 Détection et diagnostic de défaillance de ferme solaire
AU2019370621A AU2019370621A1 (en) 2018-10-31 2019-10-31 Solar farm fault detection and diagnosis

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AU2018904145 2018-10-31
AU2018904145A AU2018904145A0 (en) 2018-10-31 Fault detection in solar farms

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EP3874593A4 (fr) 2022-08-10
EP3874593A1 (fr) 2021-09-08
US20230299715A1 (en) 2023-09-21

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